1. Field of the Invention
The present invention relates to an electrically driven hand-held tool including a housing having a plurality of air suction openings, an electromotor, a gear set for transmitting rotation of an output shaft of the electromotor to a drive spindle, and a fan-wheel all arranged in the housing, with the fan-wheel providing, during operation of the tool, for aspiration of air through the suction openings for directing the aspirated air past the electromotor and the gear set for cooling the same, and for expelling warm air, which was heated as a result of absorbing heat generated by the electromotor and the gear set during the operation of the tool, out of the housing, and guide means for directing the warm air out of the housing.
2. Description of the Prior Art
In all of the conventional electrically driven hand-held tools, e.g., in screw-driving tools, the electromotor, which is arranged in the tool housing, is usually cooled by air. To this end, a fan is arranged in the housing the fan-wheel of which provides for aspiration of the air through suction openings formed in the housing. The aspirated air flows past the electromotor and the gear set provided in a drive train to the working tool. Then, the heated air is expelled back into atmosphere through blow-out openings formed in the housing. Usually, the warm air is expelled in a direction toward the tool operator which is extremely unpleasant in case the eyes of the operator are in vicinity of the blow-out openings. Further, during the operation of the tool, the air cooling is a continuous source of noise as the outgoing air transmits the noise, which is generated by the electromotor, the gear set, and, in particular, by the fan to the surrounding environment. The resulting, relatively high frequency acoustic oscillations are rather disturbing for the operator and the environment.
Accordingly, an object of the present invention is to eliminate the known drawbacks of the electrically drive hand-held tool.
Another object of the invention is to provide an electrically driven hand-held tool with which, even if the tool is held at a head height during its use, the outgoing warm air would not disturb the operator.
A further object of the invention is to provide an electrically driven hand-held tool in which the noise, which is generated by the electromotor, the gear set, and in particular, by the fan for suction of the cooling air, will be at least partially reduced.
These and other objects of the present invention, which will become apparent hereinafter, are achieved, by providing an electrically driven hand-held tool including a housing having a plurality of air suction openings, an electromotor, a gear set for transmitting rotation of an output shaft of the electromotor to a drive spindle, and a fan-wheel all arranged in the housing, with the fan-wheel providing, during operation of the tool, for aspiration of air through the suction openings, for directing the aspirated air past the electromotor and the gear set for cooling same, and for expelling warm air, which was heated as a result of absorbing heat generated by the electromotor and the gear set during the operation of the tool, out of the housing.
Downstream of the electromotor and the gear set, there is provided a warm air channel spaced from a tool handle and having a plurality of blow-out openings. The blow-out openings are arranged in such a way that during use of the hand-held tool, the expelled warm air flows in a direction away from the tool operator.
By providing a separate channel for the warm air, which is spaced from the handle, it became possible to so arrange the blow-out openings that during the use of the tool, the expelled warm air does not disturb the operator any more.
The additional channel for the warm air offers different advantageous possibilities for the tool design. E.g., in tools, in which the electromotor extends substantially vertically, with respect to the drive spindle axis, in the tool housing, the warm air channel is integrated in the housing. In this case, the blow-out openings are provided on the side of the housing remote from the handle. The warm air channel adjoins that section of the housing in which the electromotor is arranged. The handle is connected with the housing and forms with the housing section, in which the electromotor is arranged, a spade handle. The housing section, in which the electromotor is located, serves as a hand protecting member. Because the blow-out openings are provided on the side of the housing remote from the handle, the warm air is expelled in a direction away from the operator.
In the alternative embodiment, the electromotor is arranged in the housing, with respect to the drive spindle axis, substantially horizontally. Such an arrangement is used in a majority of the known hand-held tool. In this case, the warm air channel is formed in a hand protecting part that extends from the housing to the handle in a spaced relationship to the handle. The blow-out openings are again provided on the side of the hand protecting part remote from the handle. The arrangement of the blow-out openings on the side of the hand protecting part remote from the handle prevents the warm air from reaching the operator.
In one embodiment of the inventive hand-held tool with a horizontally arranged, with respect to the drive spindle axis, electromotor, the hand protecting part is formed as a separate part releasably connectable with the housing. The hand-protecting part has, at its end connectable with the housing, two spaced cheeks extendable on opposite sides of the housing. Upon connecting the hand protection part with the housing, the cheeks cover the air outlet openings which are provided on opposite sides of the housing. Openings in the cheeks provide for flow of the warm air into the warm air channel and to the blow-out openings. With the hand-protecting part being removed, the hand-held tool is similar to a conventional hand-held tool. With the pinned-up hand protecting part, guiding of the warm air away from an operator is insured. The hand protecting part can be formed as a complementary part to a conventional hand-held tool. According to a preferred embodiment of a hand-held tool according to the present invention, the hand-protecting part can be formed of two sections, a first stirrup-like section which, preferably, is fixedly connected with the tool housing, and a second pin-up section releasably connectable with the first section, with the warm air channel being formed in the second, pin-up section.
With a hand-held tool according to the present invention, there exists a possibility to provide, at least in a portion of the warm air channel, noise suppression means which permits to at least partially reduce the noise generated by the electromotor, the gear set, and in particular, by the fan.
In a relatively easy, from the manufacturing point of view, producible embodiment of a hand-held tool according to the present invention, the noise suppression means is formed as baffle plates projecting from the inner wall of the warm air channel. The warm air channel is formed of two half-shells connectable with each other. Advantageously, the half-shells are produced, at their mass production, by an injection-molding process. The warm air channel can be also integrated in the tool housing at the mass production of the tool housings which usually are also formed of two half-shells.
In an embodiment of the hand-held tool according to the present invention characterized by a high degree of noise suppression, at least a section of the warm air channel is provided with noise-absorbing material. The noise-absorbing material can, e.g., be provided in a cartridge securable in the warm air channel. The warm air flows through the cartridge.
The noise-absorbing material suppresses the accompanying sound waves. The cartridge usually has a cylindrical shape, whereby the path the warm air has to pass is extended, which improves the noise suppression action of the cartridge.
As a noise absorbing material, steel wool, mineral fibers or floculant cellular material can be used. In case a cellular material is used, it can be arranged on the inner wall of the warm air channel in form of a coating.
Because the suction openings are formed in the section of the housing spaced from a workpiece by a most possible distance, the foreign bodies produced during the tool use are prevented from being aspirated into the housing with the cooling air.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.